Sensor-net system and sensor node

ABSTRACT

A sensor-Net system includes sensor nodes which are in intermittent operation so as to save power by repeating activated state and inactivated state at a regular interval. Synchronization of time in the system is executed by aligning to the intermittent operation of the sensor nodes. A management server issues a setTime command for configuring the time to each gateway node at a specified interval. Each router node sets or corrects the time of it based on the time received from the gateway node and thereafter turns ON the time configuration flag for each sensor node in order to expand the setTime command to all of its sibling sensor nodes. The router node, upon reception of a polling, which is a command request, from the sensor node, obtains the time at that time, then uses the time to generate a setTime command to transmit to that sensor node.

CLAIM OF PRIORITY

The present application claims priority from Japanese application JP2007-151866 filed on Jun. 7, 2007, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention is related to a system using sensor nodes thatintermittently operates so as to save power by repeating activated stateand inactivated state at a regular interval, more specifically to atechnology for synchronization of time in the entire system.

ZigBee is a wireless communication method used in a conventional sensornetwork. See ZigBee standard, published by ZigBee Alliance, on theZigBee Alliance Website (URL: http://www.zigbee.org/) (searched on May21, 2007).

There is also a grid search method as a method of identifying theearthquake focus. For example, see the technical document on theoverview and processing method of the Earthquake Early Warning (EEW), onthe Japan Meteorological Agency website (URL:http://www.seisvol.kishou.go.jp/eq/EEW/kentokai5/) (searched on May 21,2007).

BRIEF SUMMARY OF THE INVENTION

Recently, the development of the Sensor-Net system is in progress, whichincorporates miniature wireless sensor nodes (referred to as sensornodes, herein below) which are equipped with sensor function, routernodes, a gateway node, as well as sensor-Net management server (referredto as management server, herein below). The sensor nodes may observe thestate of person or location (sensor data), relay thus observed sensordata through the router node in a multi-hop manner, route the datathrough the gateway node to send it to the management server. Themanagement server will perform various processes based on thus receivedsensor data.

The key device in the sensor-Net system is the sensor node, which ischaracterized by its small size and low power consumption. Because it issmall the node can be attached to anything including people andenvironment. Because it consumes low power it can operate for a periodof several years with a battery, without feeding power from an externalpower supply. Because it uses wireless communication, it can be deployedin a wide area via a gateway node or a router node.

The distinctive operation of the sensor node is its intermittentactivation. Any necessary hardware is driven only when performing suchtasks as sensing and data transmission, and when there is no task to beperformed the peripheral hardware such as the radio frequency (RF)circuit will be completely stopped, and the microprocessor will be putin a sleep, low power mode. By the intermittent operation, the sensornode is capable of functioning for a long period of time only with alimited battery power.

After the microprocessor expires its predetermined sleep period, a timergenerates an interrupt to reactivate the microprocessor to the normaloperation mode. Then, followed by a predetermined procedure, themicroprocessor executes the sensing, transmits thus sensed data, andreceives any data for it by polling to process the data. If there are nomore tasks to execute, the node reenters into the sleep mode for apredetermined period of time. The duration of task processing periodbetween two sleep periods should be tens milliseconds to one second atmaximum, therefore the sensor node is put into the sleep state in almostall of its life.

The fundamental characteristics of the intermittent operation are to“put into sleep mode when there is no task to be performed”. Theimplementation of intermittent operation may include a variety ofmethods according to the task scheduling scheme. For example, if asensor node incorporates plural sensors, then a unique sensing intervalfor each of sensors may be implemented. Since the sensing, the datatransmission, and the data reception are fundamentally independenttasks, an independent operation interval may be set for each of tasks.

One method of receiving commands from a management server in a sensornode which intermittently activates and deactivates, is the pollingmethod, in which the sender is asked for any command to that node in aregular basis. In this case no command is arrived at the sensor nodeunless the sensor node itself executes the polling. The sensor node isallowed to operate in accordance with its intermittent interval. In caseof ZigBee, the wireless communication method used in the sensor network(see non-patent reference document #1), the required time from the querypacket transmission at the time of polling to the reception of responsethereto may be approximately tens milliseconds, so that the increase ofpower consumption associated with the implementation of polling whenthere is no data will be minute.

The intermittent operation method as have been described above isindispensable technology for the low power, long life operation of thesensor node. However this may cause a disadvantage. The sensor node hasto continue sensing even when no data is reached to the managementserver by any reason, because the wireless communication is temporarilyintercepted or because the transmission is disabled by the morespecifically being shut-down, and the observation time is required evenin this case. If there is some delay on the communication route, theremay be a case in which the observation time is not matched with thereception time by the management server. To determine accurately thesensed time, it is ideal for a sensor node to provide the observationtime. To do so the sensor node should have a clock, and the clock isaccurately synchronized with the reference time. However, in case inwhich there is plural sensor nodes, the time may be set by a command,ideally. Because the sensor node intermittently operates, the commandmay not be accepted anytime. It may be possible that the managementserver issues a command at the time that the sensor node executes thepolling, but the energy efficiency in the sensor node is worse becausethe sensor node must wait for receiving the response from the managementserver and is required to be activated for a long period of time.

The present invention overcomes the problems in the conventionalintermittent operation scheme and the object of the present invention isto provide a sensor-Net system which uses an intermittent operation withbetter energy efficiency.

To solve the problems as described above, in accordance with the presentinvention, when setting time on the clocks of the gateway node, therouter node, and the sensor nodes, the router node obtains the currenttime at the time when the router node is requested to send a command bythe sensor node, then issues a time setting command to set time in thesensor node that has issued the command transmission request.

In the sensor-Net system in accordance with the present invention therouter node has a time configuration flag corresponding to each of allsensor nodes, the router node sets time by receiving the time settingcommand from the gateway node, turning on the time configuration flag atthe time when the clock in the router node is set, then confirming thestate of the time configuration flag when it receives a commandtransmission request from a sensor node, transmitting the time settingcommand only when the flag is ON, thereafter turning OFF the timeconfiguration flag at the time when it receives the response to the timesetting command.

The sensor-Net system in accordance with the present invention is asystem in which the gateway node has plural router nodes and pluralsensor nodes as siblings, and has a management table for managing thesesibling nodes. The gateway node synchronizes the router nodes by sendingfrom the management server to the gateway node a time setting command,by expanding the time setting command immediately to its sibling routernodes by referring the management table.

In the sensor-Net system in accordance with the present invention asensor node issues a time setting command at the time when it isconnected to the gateway node or at the regular interval, and invokesthe timer at the time when it receives the time request command from thegateway node. The gateway node obtains the reference time at the timewhen it receives the time request command and transmits the referencetime to the sensor node at the time when it receives the command requestfrom the sensor node. The sensor node, upon reception of the referencetime from the gateway node, stops the timer, and calculates the timerworking time from the difference between the timer stopping time and thetimer invoking time, in order to set time by adding to the referencetime the timer working time.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification illustrate an embodiment of the inventionand, together with the description, serve to explain the objects,advantages and principles of the invention. In the drawings,

FIG. 1 shows a schematic diagram illustrating the entire system of thesensor-Net in accordance with first preferred embodiment of the presentinvention;

FIG. 2 shows a schematic block diagram illustrating the hardwarearrangement in the sensor node in accordance with the first preferredembodiment of the present invention;

FIG. 3 shows a schematic block diagram illustrating the hardwarearrangement in a router node in accordance with the first preferredembodiment of the present invention;

FIG. 4 shows a schematic block diagram illustrating the hardwarearrangement in a gateway node in accordance with the first preferredembodiment of the present invention;

FIG. 5 shows a schematic block diagram illustrating the hardwarearrangement of a management server in accordance with the firstpreferred embodiment of the present invention;

FIG. 6 shows a functional block diagram illustrating the functionalarrangement of the sensor node in accordance with the first preferredembodiment of the present invention;

FIG. 7 shows a functional block diagram illustrating the functionalarrangement of the router node in accordance with the first preferredembodiment of the present invention;

FIG. 8 shows a functional block diagram illustrating the functionalarrangement of the gateway node in accordance with the first preferredembodiment of the present invention;

FIG. 9 shows a functional block diagram illustrating the functionalarrangement of the sensor-Net management server in accordance with thefirst preferred embodiment of the present invention;

FIG. 10 shows a sequential diagram for setting time between the routernode and a node in accordance with the first preferred embodiment of thepresent invention;

FIG. 11 shows a sequential diagram for setting time between the routernode and plural sensor nodes in accordance with the first preferredembodiment of the present invention;

FIG. 12 shows a PAD diagram illustrating the operational sequence of therouter node in accordance with the first preferred embodiment of thepresent invention;

FIG. 13 shows a flow chart for setting the real time clock in the routernode in accordance with the first preferred embodiment of the presentinvention;

FIG. 14 shows a flow chart at the time of command transmission of therouter node in accordance with the first preferred embodiment of thepresent invention;

FIG. 15 shows a flow chart at the time of activation of the sensor nodein accordance with the first preferred embodiment of the presentinvention;

FIGS. 16A and 16B show schematic diagrams illustrating the timecorrection in the observation value table in the sensor node inaccordance with the first preferred embodiment of the present invention;

FIG. 17 shows a time setting sequence diagram in a sensor-Net system inaccordance with the second preferred embodiment of the presentinvention;

FIGS. 18A to 18C show schematic diagrams illustrating the timesynchronization function between the sensor nodes in accordance with thesecond preferred embodiment of the present invention;

FIG. 19 show system configuration diagrams, wherein FIG. 19A illustratesan exemplary application of the sensor-Net system using the timesynchronization method in accordance with the preferred embodiment ofthe present invention for determining the influence between persons;FIG. 19B illustrates an exemplary application of the sensor-Net systemusing the time synchronization method in accordance with the preferredembodiment of the present invention for determining the influencebetween persons; FIG. 19C illustrates an exemplary application of thesensor-Net system using the time synchronization method in accordancewith the preferred embodiment of the present invention for determiningthe influence between persons;

FIG. 20 shows a system configuration diagram of the sensor-Net systemillustrating an exemplary application of the sensor-Net system using thetime synchronization method in accordance with the preferred embodimentof the present invention for identifying the focus of earthquake;

FIG. 21 shows a system configuration diagram of the sensor-Net systemillustrating an exemplary application of the sensor-Net system using thetime synchronization method in accordance with the preferred embodimentof the present invention for observing the vibration of piping; and

FIG. 22 shows a time setting sequence diagram in accordance with thirdpreferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description of some preferred embodiments will now givenwhich embody the present invention, referring the accompanying drawings.

Embodiment 1

Now referring to FIG. 1 there is shown the entire system of a sensor-Netsystem in accordance with the first preferred embodiment of the presentinvention. The sensor-Net system is made up of a management server 4equipped with a middleware for controlling the sensor nodes and managingthe association of nodes, plural gateway nodes 1, plural router nodes 2,and plural sensor nodes. The management server 4, the router node 2, andsensor node 3 are connected by wireless communication, establishing apersonal area network (PAN). The gateway node 1 and the managementserver 4 may be connected by an Ethernet or a USB (universal serialbus).

Now referring to FIG. 2, there is shown a schematic diagram illustratingan exemplary hardware configuration in the sensor node 3 used in thesensor-Net system shown in FIG. 1.

The sensor node 3 includes an RF transceiver 201 for wirelesstransmission and reception, a display 202, a button 203, a sensor(s)204, a microprocessor 205 which is the processing unit, a real-timeclock 206 which maintains the absolute time, a volatile memory 207,nonvolatile memory 208, and read-only memory 209 which serve as thestorage unit, and a battery 210 for supplying power to the components ofthe node.

The sensor node 3 may be one of either two states for a given period oftime, namely sleep mode in which all hardware is powered off except forthe real-time clock 206, and an operation mode in which all circuits arepowered on. When in the operation state the sensor node 3 senses using avariety of sensors 204. The sensed information is put into packets bythe microprocessor 205 along with the time information of the real-timeclock 206, is sent via a wireless means to the gateway node and to therouter node from the RF transceiver 201 as well as is stored in thenonvolatile memory 208.

The button 203 is an input device for accepting the operation by theuser. With a specific sequence of button a specific operation of thesensor node 3 may be invoked or the operation parameter may be set.

The display 202 is an output device for displaying information to theuser. For example, if the sensor node 3 is placed indoor or outdoor foruse as environment measurement, the latest measurement value measured bythe sensor(s) 204 may be displayed thereon. To save power, it ispreferable that the display normally is turned off but indicates thelatest measurement value only when a specific combination of button ispressed. If the sensor node 3 is a name plate type, or watch typeportable sensor node, it usually displays time but when it receives atext message from the management server 4 it may display the message orwhen it receives a voice message it may display the information ofreception. The node may display a hierarchy menu in association with thebutton sequence by the user. By pressing button in accordance with themenu, the application user or system manager may set the operationparameters of the sensor node, or confirm the error information when thecommunication is failed.

Now referring to FIG. 3 there is shown an exemplary hardware arrangementof the router node 2 in the sensor-Net system shown in FIG. 1. Therouter node includes an RF transceiver 301 for the wireless transmissionand reception, a display 302, a button 303, a sensor(s) 304, amicroprocessor 305, a real time clock 306 which maintains the absolutetime, a volatile memory 307, a nonvolatile memory 308, and a read onlymemory 309.

The router node uses the time configuration managing table 311 stored inthe volatile memory 307 to manage the path to the sibling sensor nodes.The command distributed by the wireless communication from the gatewaynode to the sensor nodes is received by the RF transceiver 301, androutes the command to the sensor nodes present in the table timeconfiguration managing table 311. Also it receives the sensinginformation transmitted by the wireless communication from a sensor nodeto transmit thus received sensing information to the gateway node by thewireless communication.

The router RT1 is required to always wait for the data from the sensornode or the gateway node, but does not know when the data is sent, sothat it operates by the external power instead of a battery unlike thesensor node. The power supplied through the power line is rectified by apower supply circuit 310 to provide to the components.

Since the router node 2 does not need to be worried about theconsumption power, the microprocessor 305 of the router node 2 is notrequired to be put into the sleep mode, unlike the sensor node 3. Theinterrupt controller and timer, which are not shown in the figure,thereby have the function used in the limit of generic data transmissionand reception algorithm.

Now referring to FIG. 4 there is shown an exemplary hardware arrangementof the gateway node 1 used in the sensor-Net system shown in FIG. 1.

The gateway node has the similar components to the router node 2 exceptfor having a LAN interface (LAN I/F) 412 for communicating with themiddleware server 4 through an IP network, the detailed descriptionthereof will be omitted. In the figure the reference numbers 401 to 410correspond to the reference numbers 301 to 310 in FIG. 3. In thevolatile memory 407 there is stored a binding table 411 as will bedescribed later.

Now referring to FIG. 5 there is shown a schematic block diagramillustrating an exemplary hardware arrangement of the sensor-Net systemmanagement server 4 shown in FIG. 1.

The sensor-Net management server 4 includes a processor (CPU) 501, acommunication unit 502, a power supply 503, a hard disk drive 504, akeyboard 505 which is an input device for a user to input a command, adisplay 506, and a memory 507.

The sensor-Net management server 4 receives through the communicationunit 502 the data collected by the gateway node 1 from the sensor node 1through the router node 2, and transmits the commands to the gatewaynode 1. The CPU 501 reads such programs as middleware stored in thememory 507, processes, by the instruction of the program, such data asthe observation values obtained through the communication unit 502,stores the data to the hard disk drive 504, or displays the data ontothe display 506. A more specific example of processing and displayexecuted by the management server 4 will be described in greater detailslater. The CPU 501 interprets the user command input from the keyboard505 to transfer through the communication unit 502 to the gateway node1.

Now referring to FIG. 6 there is shown a schematic block diagramillustrating the functionality of the sensor node 3 in the preferredembodiment.

The function of the sensor node 3 includes, the real-time clock 206 formanaging the time, a main unit 601 for storing the observation value andfor managing the event publishing and polling publishing, an observationunit 602 for using the sensor(s) for the observation, an event publisherunit 604 for publishing an event such as the observation value, apolling publisher unit 605 for publishing to the router node 2 or to thegateway node 1 the polling to confirm whether a command is present ornot, a transmitter unit 606 for transmitting an event or a polling, anobservation value storage management unit (event storage unit) 607 formanaging the storage of observation values, an observation value storageunit 603 for storing the observation values and managing by theobservation value table 613, an observation value time stamp correctionunit 608 for correcting the time stamp of the observation values whichhas the time unconfirmed flag set to ON (a flag which means theobservation time is unconfirmed) in the observation value table 613, anRTC setting unit 609 for setting and correcting the real time clock, areceiver unit 610 for receiving commands from the parent router node orthe parent gateway node, a command analyzer unit 611 for analyzingreceived commands, and an other commands processing unit 612 forprocessing any other commands than the time setting.

The observation value table 613 stored in the observation value storageunit 603 stores the sequence number 614 which is the serial number ofthe observation values, a time unconfirmed flag 615 which stores whetherthe time is confirmed or unconfirmed in an observation value, anobservation value 616, and the time of the observation value 617. In thehardware configuration of the sensor node 3 as shown in FIG. 2, theobservation value storage unit 603 is formed on the nonvolatile memory203.

The transmitter unit 606 and the receiver unit 610 shown in FIG. 6correspond to the RF transceiver 201 shown in FIG. 2. Other componentsincluding the main unit 601, the observation unit 602, the eventpublisher unit 604 to the RTC setting unit 609, the command analyzerunit 611, the other commands processing unit 612 are program functionsexecuted by the microprocessor 205 of FIG. 2, these programs are storedin general on the storage unit such as the read-only memory 209.

Now referring to FIG. 7 there is shown a schematic block diagramillustrating the function of the router node 2 in accordance with thepreferred embodiment of the present invention.

The router node 2 includes a command receiver unit 701, a timeconfiguration processing unit 1301, and a command transmissionprocessing unit 1401, a command request receiver unit 707, a commandpublisher unit 708, and a real-time clock 306. The time configurationprocessing unit 1301 includes a time configuration manager unit 703 anda time configuration manager unit 702. In the command transmissionprocessing unit 1401 there are a time configuration status checking unit706 and a time obtaining unit 705. The volatile memory 307 shown in FIG.3 has a time configuration managing table 311. In the time configurationmanaging table 311 the sensor node ID 709 each allocated for each sensornode, and a time configuration flag 710 for determining whether or notthe sensor node in the node ID 709 has the time configured.

The router node 2 receives the command transmitted from the managementserver 4 at the command receiver unit 701. When the received command issetTime command, the time setting unit 702 for setting or correcting thetime of the real time clock 306 and the time configuration manager unit703 for setting On the time configuration flag of the sensor noderegistered in the time configuration managing table 311 will work.

The polling command from the sensor node 3 is received by the commandrequest receiver unit 707. The time configuration status checking unit706 will check to see the time configuration flag 710 of the sensor nodewhen receiving the polling from the sensor node in the timeconfiguration managing table 311. The time obtaining unit 705 obtainsthe time from the real time clock 306. The command publisher unit 708publishes a command to the sensor node 3. These functions are, needlessto say, of the program sequentially executed in the microprocessor 305shown in FIG. 3, and this applies to the following description as well.

Now referring to FIG. 8 there is a schematic block diagram illustratingthe function of the gateway node 1 in accordance with the preferredembodiment of the present invention.

The function of the gateway node 1 includes a wired communication unit801 for communicating with the management server 4, a command processingunit 805 for processing commands from the management server 4, a timeconfiguration unit 806 for setting the real time clock 806 in thegateway node 1, a setTime processing unit 807 for referring the bindingtable 411 to process the setTime command when receiving the setTimecommand, a command publisher 804 for publishing the command to thesibling router node 2 or to the sibling sensor node 3 present in thebinding table 411, a wireless communication unit 803 for wirelesscommunication with the router node 2 and the sensor node 3, and an eventprocessing unit 802 for processing events received from the router node2 or the sensor node 3. In the binding table 808 a node categoryrecorder 809 for storing the category by determining whether therecorded node is a router or a sensor node, and a node ID 810 eachprovided for each node are stored.

Now referring to FIG. 9, there is shown a schematic block diagramillustrating the network management function of the sensor-Netmanagement server 4 in accordance with the preferred embodiment of thepresent invention.

The network management function of the management server 4 includes atime configuration management unit 902, an external request receiverunit 901 for receiving a user command 910 and for transferring to thetime configuration management unit 902 or to the action manager 906 andtransmitting the response to the external entity, a timer 904 forsynchronizing with a reference time 903 such as NTP (network timeprotocol) to issue a setTime command at a given time, a setTime commandpublisher 905 for issuing the setTime command, a sensor-Netcommunication unit 907 (Profiled adapter & ZigBee adapter) whichcorresponds to the communication unit 502 for communicating with thegateway node 1, an event publisher 908 for transferring the event fromthe gateway node 1, or the router node 2, or the sensor node 3, and anobservation value storage unit 909 for storing the observation value ofthe sensor node 3. The observation value storage unit 909 is formed onthe storage unit such as the hard disk drive 504 or the memory 507 inFIG. 5, and the function units except for the observation value storageunit 909 and the sensor-Net communication unit 907 are configured as theprocessing function of the CPU 501 shown in FIG. 5.

Now the time synchronization of the entire system by using theconfiguration and function of these devices in the sensor-Net system inaccordance with the preferred embodiment of the present invention willbe described in greater details below.

Now referring to FIG. 10, there is shown a time configuration sequencediagram between the router node 2 and the sensor node 3 (sensor #1) whenthe sensor node 3 (sensor #1) is intermittently operating at theinterval of 10 minutes. Any other operations except for the timeconfiguration such as observation are omitted in this figure becauseFIG. 10 only illustrates the time configuration sequence.

When the sensor #1 returns from the sleep mode 1012 and enters into theactive mode 1006, the sensor #1 will poll 1007 the parent router node 2.At this time the router node 2 has not received yet any setTime, and thetime configuration flag 710 in the time configuration managing table 311is OFF (displayed as white in the figure). The router node transmits ano command present 1008 as the response to the polling 1007. The sensor#1 upon reception of the response immediately moves to the sleep mode1013. The duration of the active period 1006 may be in the range from afew milliseconds to tens milliseconds, including the polling and thereception of the response.

Thereafter, the router node 2, which receives the reference time 1001issued by the management server 4, will set or correct the real timeclock 306 of the router itself, then set to ON the time configurationflag 710 of the sibling sensor nodes 3 registered in the timeconfiguration managing table 311 (displayed as gray in the figure). Therouter node 2, when receiving a command request as polling 1007 from thesibling sensor node (sensor #1) which is registered in the timeconfiguration managing table 311, confirms the time configuration flag710, and if the flag is ON, then it will respond with a command present1009, obtains the time from the real time clock 306 of the router itself(step S1006), transfers the time (t2) to the sensor #1 as the setTimecommand 1010. Thereafter the sensor node 3 turns OFF the timeconfiguration flag 710 of the sensor node. The sensor #1, upon receptionof the response to the command present 1009, will wait for a while in astand-by state, then will correct, based on the received time (t2), thetime of the real-time clock 206 of the sensor node itself. The activeperiod 1014 of the sensor #1 at this time may be longer than the activeperiod 1006 because the sensor node receives the setTime command toreconfigure the time, however the period may be in the range from 10milliseconds to 50 milliseconds on total, which is an instant whencompared with the duration of sleep period which is 10 minutes.

Now referring to FIG. 11, there is shown a time configuration sequencediagram between the management server 4 and the gateway node 1 and therouter node 2 and two sensor nodes 3. The time configuration sequencewill be similar even if there are more than three sensor nodes 3.

The sensor #1, which returns from the sleep period 1106 and enters intothe active period 1107, will poll 1007 to the parent router node 2. Atthis time the router node 2 has not received yet any setTime command,and because the time configuration flags 710 in the time configurationmanagement table 1111 are all OFF, the router node 2 will transmit a nocommand present 1008 as the response to the polling 1007 to the sensor#1. The sensor #1, which has received the response thereto, willimmediately enter into the sleep mode 1108. The duration of the activeperiod 1107 may be in the range from a few milliseconds to tensmilliseconds, including the polling and the reception of the responsethereto. A sensor #2, in a similar manner, which returns from the sleepmode and enters into the active period 1111, will send a polling 1103 tothe parent router node 2. The router node will respond the no commandpresent 1104 to the sensor as was done in case of the sensor #1, and thesensor #2, upon reception of the response thereto, will immediatelyenter into the sleep mode 1112.

The management server 4, as have been described above, is synchronizedwith a reference time by NTP. The management server 4 sends a time (t1)as the setTime command to the gateway node 1 at a regular basis, or atthe time specified by the user. The gateway node 1 uses thus receivedtime (t1) to set or correct the real time clock 406 of the stationitself (1101). The gateway node 1 will confirm the binding table 808,which is a management table of the nodes reachable from the gatewaynode, at the same time as the real time clock configuration 1101, andtransmits the time (t1) obtained from the management server 4 as thesetTime command to the sibling routers registered in the table. Althoughthere is shown only one router node 2 in FIG. 11, the time issynchronized by transmitting the time (t1) to all routers in a similarmanner if there are plural routers registered in the table.

The router node 2 will set or correct the real time clock 306 in therouter itself based on the time (t1) received from the gateway node(1301), then set to ON the time configuration flag 710 to all siblingsensor nodes registered in the time configuration managing table 311.The sensor node 3 a (sensor #1), immediately after returned from sleepperiod 1108, will perform the observation (1102), then send a polling1107 as the command request to the router node 2. The parent router node2 of the sensor #1, upon reception of the polling 1107 as the commandrequest from any one of the sibling sensor nodes registered in the timeconfiguration managing table 311, will confirm the time configurationflag 710 of the sensor node, and respond with a command present 1009 ifthe flag is ON, and obtains (S1406) the time from the real time clock306 of the router node 2 itself to send the time (t2) as the setTimecommand. Thereafter, when it receives an Ack which is the response tothe setTime command from the sensor #1, the router turns OFF the timeconfiguration flag 710 of the sensor node. At this time the activeperiod 1109 of the sensor #1 will be longer than the active period 1107,because the sensor #1 receives the setTime command and set the time,however the period may be in the range from 10 milliseconds to 50milliseconds, including the processing time of polling, timeconfiguration reception, sending an observed event (1105), and receivinga reply (Ack), so the active period may be an instant when compared with10 minutes of the duration of the sleep period.

The sensor node 3 b (sensor #1) upon reception of the reply to thecommand present 1009, will wait for a while in a stand-by state, thencorrect the time in the real-time clock 206 of the sensor node itselfbased on the received time (t2). The sensor #1 obtains the time from itsreal time clock 206 and attaches it to the observation value for sendingto the router node 2 as an observed event (1105). The sensor node 3 b(sensor #2) will perform a similar sequence as the time configurationsequence of the sensor #1.

Although not shown in FIG. 11, there may be cases in which plural sensornodes 3 are directly connected to the gateway node 1. In such a case thesequence between the gateway node 1 and a sensor node 3 is justidentical, with the router node 2 being replaced with the gateway node 1in the sequence between the router node 2 and the sensor node 3, inwhich the gateway node 1 and the sensor node 3 will behave in a similarmanner.

Next, referring to FIG. 12 there is shown a PAD diagram of the operationof the router node 2 in accordance with the preferred embodiment of thepresent invention.

The router node 2 will perform an event transfer 1203 for transferringto the gateway node 1 if the received data is an event such as theobservation value from the sensor node 3, a command transmission 1401 incase of polling from the sensor node 3, a time configuration processing1301 when having received a setTime command from the gateway node 1, anda command storage 1204 when receiving any command other than the timeconfiguration.

Now referring to FIG. 13 there is shown a time configuration sequencediagram in the time configuration processing unit 1301. The router node2 receives in the command receiver unit 701 a setTime command throughthe gateway node 1 from the management server 4 (step S1302). Then thetime configuration unit 702 will set the real time clock 306 of therouter itself to the time described in the setTime command (step S1303).Then the time configuration manager unit 703 turns ON all timeconfiguration flags 710 of the sibling nodes which are managed in thetime configuration managing table 311 (step S1304), and the processterminates (step S1305).

Now referring to FIG. 14 there is shown a command transmission sequenceof the router node 2. The router node 2, upon reception of a polling,the command request from the sensor node 3, at the command requestreceiver unit 707, will determine whether there is a stored command(step S1402), and if there is a command then it will send a commandpresent to the sensor node (step S1404). Thereafter, the timeconfiguration status checking unit 706 will determine the timeconfiguration flag 710 of the sensor node in the time configurationmanaging table 311 (step S1405), and if the flag is ON then the timeobtaining unit 705 will obtain the current time from the real time clock306 of the router node 2 (step S1406), will send a setTime command fromthe command publisher unit 708 (step S1407), then will turn off the timeconfiguration flag of the sensor node (step S1408), and will check tosee if there is still another command stored therein (step S1402). Ifthe time configuration flag 710 is OFF, then it will send another storedcommand (S1409), and will check to see if there is still another commandstored therein (S1402). If there is no more command stored for thesensor node, it will send no command present to the sensor node (stepS1403), and the process terminates (S1410).

Now referring to FIG. 15 there is shown a flow chart of the operation ofthe sensor node 3 in accordance with the preferred embodiment of thepresent invention.

The sensor node 3 intermittently operates, in which it repeats theactivation to enter into the active state (S1501) and the deactivationto enter into the sleep state (S1514) at a regular interval. For theactivation interval, an independent period may be set for any sensors ifa sensor node is equipped with plural sensors 204. When the sensor node3 is activated, it will observe (S1502) in the observation unit 602 asshown in FIG. 6, issue a polling from the polling publisher unit 605,then send the polling from the transmitter unit 606 to the parent routernode 2 (S1503). It will receive the reply from the router node 2 by thereceiver unit 610, will determine whether there is either a commandpresent or a no command present (S1504), and will receive the command ifthere is a command present (S1505). The command analyzer unit 611 willdetermine whether the command received is a setTime command or not(S1506), if it is a setTime command then the RTC setting unit 609 willset or correct its real-time clock 206 (S1507), then the observationvalue time stamp correction unit 608 will correct the time stamp of anyobservation values with the time unconfigured flag being ON, from withinany previous observation values in the observation value table 613 (stepS1508). If the received command is not a setTime command then the othercommands processing unit 612 will process the command (S1509).

After finishing the processing of the command, the sensor node 3 willdetermine whether it has already time configured (S1510), if the time isconfigured then the event publisher unit 604 will issue an event withthe current time appended as time stamp to the observation value, thenthe observation event will be sent to the parent router node 2 or to theparent gateway node 1 from the transmitter unit 606 (step S1512). If thesensor node 3 is not yet time configured then the observation value willnot be sent, however a HeartBeat event will be sent to the parent routernode 2 or to the parent gateway node 1 in order to notify of the alivesensor node 3 (S1511).

After the transmission of the event, the sensor node 3 stores theobservation value into the memory along with the sequence number, timeunconfigured flag, and the time of real time clock (S1513), and willenter into the sleep mode (step S1514).

Now referring to FIGS. 16A and 16B, there are shown schematic diagramsillustrating the time stamp correction (S1508) of the observation valuetable 613 in the sensor node 3 shown in FIG. 15. FIGS. 16A and 16Billustrate examples of data in the observation value table 613 in thesensor node 3 before and after correction of the time stamp,respectively.

The sensor node 3 calculates the difference between the time stamp ofthe latest observation value and the time in the setTime command, at thetime when it receives the setTime command from its parent router node 2or the parent gateway node 1 and configures the time. Then by referringto the observation value table 613 of the sensor node, it will correctthe time by adding the difference to the time stamp of the observationvalue with the time unconfigured flag being ON, then will turn OFF thetime unconfigured flag to correct the time stamp of the observationvalue.

The difference as have been described above may also be the differencebetween the time in the setTime command and the time before correctingthe real-time clock 206 at the time of reception of the setTime command.the correction timing of the time stamp may be at any given time afterthe calculation of the difference.

The observation event including the observation value data, sent fromthe transmitter unit 606 of the sensor node 3 to the parent router node2 or to the parent gateway node 1, will be all transferred to themanagement server 4, stored in the observation value storage unit 909 inthe storage unit of FIG. 5 or FIG. 9, then will be processedappropriately as an example will be described later.

Embodiment 2

A sensor-Net system which adopts another time synchronization method asshown in FIG. 17 will be described in greater details herein below assecond preferred embodiment of the present invention.

Now referring to FIG. 17 there is shown a schematic diagram illustratinga sensor node initiative time configuration sequence which implementsthe time synchronization at the timing requested by a sensor node 3,when the sensor node 3 (sensor) is connected directly to the gatewaynode 1. The sensor node 3 sends a time configuration request (1701) tothe gateway node 1 when connected to the gateway node 1 or at a regularbasis. The gateway node 1 will send an Ack 1702 to the timeconfiguration request while obtaining the reference time information(1703). The time required for the gateway node to obtain the timeinformation after having received the time configuration request may beapproximately one millisecond.

The sensor node 3 invokes its internal timer at the time when itreceives the Ack to the time configuration request (1704). Since theprocessing time required for the sensor node 3 to receive theacknowledgement after the gateway node 1 sends the acknowledgement isapproximately one millisecond, this time may be considered to beapproximately the same duration as the time required for the gatewaynode 1 to receive the time configuration request and to set the time.

The time as have been described above is the timer built-in to themicroprocessor within the sensor node 3. For example in case of H8S/2215of Renesas Technology Corp., the time accuracy is 1 ppm, so the errorfor setting time may be neglected. However some processing than the timeconfiguration by interrupt are needed, so that the time accuracy is 10milliseconds. In the sleep period the microprocessor is sleeping in thelow power mode while the timer operation continues to be executed.

When the sensor node 3 transmits a polling command, the command request,at the time when it is reactivated for the next time (1704), the gatewaynode 1 in turn transmits to the sensor node 3 the time obtained assecond setTime command for the reply thereto (1705). The sensor node 3stops the timer at the time when it receives the second setTime commandfrom the gateway node 1 (1708), it sets its own real-time clock 206 ascurrent time by the time adding the time received concurrently with thesecond setTime command with the time measured by the timer (1709).

By setting the time as have been described above, the sensor nodes 3with the time synchronized with the gateway node 1, in a similar mannerto FIG. 11 in the first preferred embodiment, will send the storedobservation values to the gateway node 1 directly. The detaileddescription will be omitted however to avoid the repetition.

Now referring to FIGS. 18A to 18C, there are shown an applied systemfunction for determining the influence between plural persons eachwearing a sensor node by using the sensor-Net system based on the timesynchronization scheme as described above and by using the observationvalue data stored in the observation value storage unit 909 of themanagement server 4. As shown in FIG. 18A assuming that more than twopersons 1801 and 1802 have or wear the sensor nodes 3 a and 3 b. Forexample, a person 1802 is considered to be affected by another person1801 if during a conversation between the person 1801 and the person1802, the person acts a gesture such as the person nods for expressingthe accordance with an important speech of the observation valuewaveform 1801, or the person 1802 gives a grunt or writes down thephrase in accordance with the speech of the person 1801. In addition,there may be a negative influence if one goes away from the other. Suchaction or speech may not be randomly present, rather as shown in block1803 of FIG. 18C, it appears on the observation value waveform of theacceleration or voice of the person 1802 after a delay less than asecond from the observation of the speech or action by the observationvalue waveform of the acceleration or voice of the person 1801.

From the above fact, between sensor nodes 3 of FIG. 18B, by determiningthe correlation of the action in the time axis between the dialogistsfrom the sensor signals from the sensor nodes 3 a and 3 b, which aresynchronized for example at the precision of 100 milliseconds, thecommunication between the dialogists may be given. The observationvalues synchronized between the sensor nodes 3 will be thereforeimportant, and as the synchronization scheme used for the context thetime synchronization scheme is to be adopted as have been describedabove. In the following applied system description, it is assumed that,under the time synchronization scheme adopted as have been describedabove, the sensor nodes try to synchronize at the required precision.

Now referring to FIG. 19A, FIG. 19B, and FIG. 19C there are shownschematic diagrams illustrating the flow of process for executing theorganization dynamics analysis by performing the process of determiningthe communication by means of the applied system.

More specifically, FIG. 19A, FIG. 19B, and FIG. 19C describe asequential flow from obtaining the organization dynamics data by pluralsensor nodes 3 to showing the connection between persons and the currentorganization evaluation (performance) as the organization activity.

In this embodiment the organization dynamics data obtainment (BMA), theinput of performance (BMP), the organization dynamics data collection(BMB), mutual data alignment (BMC), the correlation coefficient learning(BMD), organization activity analysis (BME), and the organizationactivity representation (BMF) are executed in an appropriate order.

Now the organization dynamics data obtainment (BMA) will be described ingreater details. The sensor node 3A (TRa) shown in FIG. 19C includessuch sensors as an acceleration sensor (TRAC), an infrared transceiver(TRIR), and a microphone (TRMI), a microcomputer (not shown in thefigure) and a wireless transmission function. The sensors detect avariety of physical quantities, and obtain the observation dataindicating thus detected physical quantities. For example, theacceleration sensor (TRAC) detects the acceleration of the sensor node3A (TRa), namely the acceleration of the person A (not shown in thefigure) wearing the sensor node 3A (TRa). The infrared transceiver(TRIR) detects the face-to-face status of the sensor node 3A (TRa),namely the status in which the sensor node 3A (TRa) is in face toanother sensor node 3. The fact that the sensor node 3A (TRa) faces withanother sensor node 3 indicates that the person A wearing the sensornode 3A (TRa) is facing with another person wearing another sensor node3. The microphone (TRMI) detects the voice around the sensor node 3A(TRa). The sensor node 3A (TRa) may also have other sensors (such asincluding a temperature sensor, a luminance sensor, etc.).

The applied system in this example includes plural sensor nodes 3 (morespecifically the sensor node 3A (TRa) to sensor node 3J (TRj) of FIG.19C). These sensor nodes 3 are each worn by the respective person: forexample, the sensor node 3A (TRa) is worn by the person A, the sensornode 3B (TRb) by the person B (not shown in the figure), and so on. Thisis for analyzing the connection among the persons wearing the sensornode and for displaying the performance of the organization.

The sensor node 3B (TRb) to sensor node 3J (TRj) also include sensors, amicrocomputer, and a wireless transmitter as similar to the sensor node3A (TRa). In the following description, these sensor nodes arecollectively referred to as sensor node 3 (TR) in case when thedescription applies to all of sensor node 3A (TRa) to sensor node 3J(TRj), and when there is no need to distinguish each sensor node 3.

Each sensor node 3 (TR) performs sensing by sensors all the time (orrepeatedly at a short interval). Then each sensor node 3 (TR) transmitsthe obtained data (sensing data) via the wireless communication at agiven interval. The interval of transmission of data may be the same asthe sensing interval, or may be a larger interval than the sensinginterval. The data to be sent at that time includes the time of sensing,and the intrinsic ID of the sensor node 3 (TR). The wirelesstransmission of the data at once is for the purpose of maintaining theextended life of the sensor node 3 (TR) as long as possible while beingworn by a person, by saving the consumption of power used for thetransmission. In addition, it is preferable that the same sensinginterval is set in all of the sensor nodes 3 (TR) for the purpose of thefollowing analysis.

The performance input (BMP) shown in FIG. 19C is the process ofinputting the value indicating the performance. The performance hereinis an objective or subjective evaluation determined based on some sortof reference. For example, the person wearing the sensor node 3 (TR)inputs at a predetermined timing a subjective evaluation (performance)value based on some sort of reference, such as the achievement of thework at that time, the contribution and satisfaction to theorganization, and so on. The predetermined timing herein may be once fora few hours, once a day, or each time an event such as a conference isover. The person wearing the sensor node 3 (TR) operates the sensor node3 (TR) or operates a personal computer (PC) such as a client (CL) toinput the performance value. Or the values written by hand may be inputat once later by using a PC. The input performance value is used forlearning the correlation index. Once a sufficient quantity ofperformance values is obtained for learning at a given level, there isno need of input further values.

The performance with respect to the organization may also be calculatedfrom the performance of individuals. The objective data including suchas the sale and cost, as well as the data already digitized such as theresult of a questionnaire of clients may also be input as performance ata regular interval. If the numerical data can be automatically obtainedsuch as the error rate in the production management, thus obtainednumeric values may be automatically input as the performance value.

The data transmitted via the wireless communication from the sensor node3 (TR) is gathered by the organization dynamics data collection (BMB)shown in FIG. 19C, and stored in a database. For example, for eachsensor node 3 (TR), or for each person wearing a sensor node 3 (TR), adata table is created. The collected data is classified based on theintrinsic ID, and is stored in the data table in the order of sensedtime. In case that the table is not created for each sensor node 3 (TR),there must be a column indicating the ID information or the personwearing the sensor node 3 (TR) in the data table. The data table A(DTBa) in the figure describes a simplified version of an exemplary datatable.

The performance value input in the performance input (BMP) is stored inthe performance database (PDB) along with the time information. The datatable database gathered in the organization dynamics data collection(BMB) is stored sequentially in the storage unit shown in FIG. 5.

Next, in the mutual data alignment (BMC) shown in FIG. 19C, to comparethe data with respect to two given persons (in other words the dataobtained by the sensor node 3 (TR) worn by these persons), the data withrespect to these two persons based on the time information is aligned.The aligned data is stored in the table. In the data with respect tothese two persons, the data having the same time is stored in the samerecord (row). The data having the same time, indicates two items of dataincluding the physical quantities detected by two sensor nodes 3 (TR) atthe same time. If the data with respect to these two persons does notinclude the data of the same time, the data of the nearest time may beused approximately as the data of the same time. In this case the dataitems of the nearest time are stored in the single same record. It ispreferable that the time of the data items stored in the same recordshould be aligned to the mean value of the nearest time. These dataitems may be stored so as to be capable of comparing chronologically thedata, and may not be necessarily in the table.

The connection table (CTBab) shown in FIG. 19C is a simplifiedexpression of the exemplary table connecting the data table A (DTBa)with the data table B (DTBb). It should be noted here that the detailsof the data table B (DTBb) is not shown in the figure. The connectiontable (CTBab) includes the data of acceleration, infrared, as well asvoice. However the connection table for each kind of data, for examplethe connection table including only the acceleration data, or theconnection table including only the voice data may also be created.

Next, in the present embodiment, the learning of the correlation index(BMD) is executed for calculating the relationship from the organizationdynamics data or for predicting the performance (see FIG. 19B).

The correlation index learning (BMD) is a process for determining thecommunication. For example, there are cases in which someonecommunicates with gestures such as nodding for an important speech ofthe other person during conversation. The action is not at random, butis taken at a given timing. The timing here is just after the speech orgesture of the other person.

From these facts, by determining the correlation of actions in the timeaxis of the dialogists who wear the sensor node from the sensor signalswhich are synchronized observation values between the sensor nodes 3,the communication between these individuals may be determined so that itis clear that the observation value data synchronized between the sensornodes 3 is important.

One speaker 1801 wears the sensor node 3 a (sensor #1) and the otherspeaker 1802 wears the sensor node 3 b (sensor #2). In this context thegateway node 1 sends a setTime command to these two sensor nodes tosynchronize with error less than for example 10 milliseconds. In FIGS.18A to 18C, there are only two speakers, however there may be pluralspeakers. In such a case some combinations covering all from within allthe speakers are specified and the process is executed for eachcombination.

Next, the process flow for the correlation learning by using the systemshown in FIGS. 18A to 18C is shown in the correlation index learning(BMD) of FIG. 19B. The process is more effective if the correlationindex is updated by recalculating regularly based on the new data. Inthe following description the correlation index is calculated from theacceleration data. The correlation index can be calculated in a similarprocedure by using the time-series data such as voice data instead ofthe acceleration data.

In the present embodiment, the correlation index learning (BMD) shown inFIG. 19B is executed in the management server 4 described with referenceto FIG. 5 and FIG. 9, more specifically in the CPU 501 thereof. Howeverin practice the correlation index learning (BMD) may also be executed byany other device than the management server 4.

First, the management server 4 will set the width T of data used forcalculation of the correlation index to a range from a few days toseveral weeks and will select the data within the range.

Then the management server 4 will execute the acceleration frequencycalculation (BMDA). The acceleration frequency calculation (BMDA) is aprocess for determining the frequency from the acceleration data alignedin the time series. The frequency is defined as the number ofoscillation of a wave in one second, this index indicates the intensityof the oscillation. However, to determine a precise frequency it isneeded to perform a Fourier Transformation, requiring a significantamount of calculation. Although the frequency may be determinedpositively by using the Fourier Transform, in the present embodiment thezero-cross data is used instead, which correspond to the frequency, inorder to simplify the calculation.

The zero-cross data is the number of times that the values in thetime-series data for a predetermined period of time become zero, moreprecisely, the count of the number of times that the time-series datavaries from a positive value to a negative value or from a negativevalue to a positive value. For example, when determining one cycle asthe value of the acceleration have changed from the positive side to thenegative side, then the value again have changed from the negative sideto the positive side, the number of oscillations for one second can becalculated from the number of times of counted zero-crossing. The numberof oscillation thus calculated for one second may be used as anapproximated frequency of the acceleration.

In addition, since the sensor node 3 (TR) of the present embodiment hasa triaxial acceleration sensor, one single zero-crossing value may becalculated by adding the zero-crossing values in the triaxial directionsof the same period of time. This allows detecting the fine motion ofpendulum in the left-right and front-back direction to use as the indexindicative of the intensity of the oscillation.

A “predetermined period of time” for counting the zero-crossing data maybe set to a value larger than the interval of contiguous data (i.e., theoriginal sensing interval), in a range of seconds or minutes.

The observation values used for the analysis are preferably of the sametime width in the speaker 1801 and in the speaker 1802, for example thevalues in a day (24 hours). The observation values are furtherpreferably continuously or periodically substituted, and when anobservation value is missing a value indicative of the absence such asNULL may be substituted therewith.

Framing (BMDB) is a process for splitting the time width of theobservation values into plural uniform widths. For example, in case ofthe observation value time width for a day (24 hours), a frame of onehour or so is preferable. The size of the width split is referred to asframe length. As there are plural sensor signals in the input sensorsignal, the timing and the width of splitting into a frame (framelength) is always the same. In addition, the span between two frames maynot be necessarily needed to set to the same time of frame split. Forexample, in case of six minutes of interval between two frames (frameinterval), the interval of 6 minutes indicates that the interval fromthe start time of the first frame to the start time of the next frame issix minutes.

Then, the cross-correlation calculation (BMDC) is determined for eachframe of the input observation values. The cross-correlation indicatesthe relationship of two time varied sensor signals. The crosscorrelation index between two observation values may be defined asfollows:

$\begin{matrix}\left( {{Equation}\mspace{20mu} 1} \right) & \; \\{{R(t)} = {{\frac{1}{T^{\prime}} \cdot \frac{\int_{0}^{T^{\prime}}{\left\{ {{x_{A}(t)} - \overset{\_}{x_{A}}} \right\} \left\{ {{x_{B}(t)} - \overset{\_}{x_{B}}} \right\} {t}}}{\begin{matrix}\sqrt{\int_{0}^{T^{\prime}}{\left\{ {{x_{A}(t)} - \overset{\_}{x_{A}}} \right\}^{2}{t}}} \\\sqrt{\int_{0}^{T^{\prime}}{\left\{ {{x_{B}(t)} - \overset{\_}{x_{B}}} \right\}^{2}{t}}}\end{matrix}}}\mspace{25mu} \begin{pmatrix}{T^{\prime} = {T - r}} \\{r = {{- T} \sim T}}\end{pmatrix}}} & (1)\end{matrix}$

x_(A(t)): Value of the feature x₁ at the time t of the person

$\frac{A}{x_{A}}\text{:}$

mean value of the feature x₁ of the person A in the range of time from 0to T

Prior to determining the cross-correlation index, the observation valuesincluded in the frame are checked to see for improving the precision ofthe cross-correlation index. This is done by counting the number of twosensor signals which are not defected in the same period of time usedfor the process of the cross-correlation index, determining the rate ofthe defects, then skipping the cross-correlation index process for theframes which has a high defect rate. The threshold of the defect ratemay be specified separately.

Finally, as in the cross-correlation index a number of values will beoutput, a value is needed which may look down upon the entire range.Then, the look down process (BMDD) is performed by determining the meanof the cross-correlation index determined for each frame in the inputobservation values in order to determine the correlation matrix (BMDE).Next, the correlation matrix (BMDE) is used for predicting sixperformances from the acceleration data.

The organization activity analysis (BME) shown in FIG. 19A is a processfor determining the connection between two individuals from theacceleration, voice, face-to-face data with respect to two givenindividuals in the connection table, and for calculating the performanceof the organization. This process also is performed by the managementserver 4, more specifically by the CPU 501.

The organizational performance is predicted and presented to users inreal-time basis while collecting data, to for example prompt so as tochange the behavior to a better direction if the prediction is worse.Briefly the feedback may be possible for a shorter cycle.

Now the calculation using the acceleration data with reference to FIG.19A will be described in greater details. The acceleration frequencycalculation (EA12), the personal feature extraction (EA13), thecross-correlation calculation between individuals (EA14), and theorganizational feature calculation (EA15) use the similar procedure tothe acceleration frequency calculation (BMDA), the personal featureextraction (BMDB), the cross-correlation calculation (BMDC) and theorganizational feature calculation (BMDD) in the correlation indexlearning (BMD), and the detailed description will be omitted. Byfollowing the procedure the organizational features (x1, . . . , xm)will be calculated.

The management server 4 then obtains the organizational features (x1, .. . , xm) calculated in step EA15 and the correlational index (A1, . . ., A6) with respect to the performances calculated by the correlationindex learning (BMD) (step EA16), then uses these values to calculatethe index of performances, as follows:

(Equation 2)

p ₁ =a ₁ x ₁ +a ₂ x ₂ + . . . +a _(m) x _(m)  (2)

This value indicates the predictive value of the organizationperformance (EA17).

As will be described later, the latest values of six indices indicativeof the organization performances are balance displayed. Further, thehistory of an index value is displayed in a time-series graph as theindex prediction history.

The distance between the given individuals, which is determined based onthe cross-correlational values between the individuals (EK41) may beused for determining the parameters for indicating the organizationstructure (organizational structure parameters). The distance betweenindividuals is an index indicative of the connection between theseindividuals, rather than the geographical distance. For example, thestronger the interpersonal relationship is (for example, the strongerthe cross-correlation between the individuals), the nearer theinterpersonal distance. By executing the grouping (EK42) based on thedistance between the individuals the group in the display may bedefined.

The grouping is a process for creating the combinations of individualsin an intimate relation, such as creating one group of at least twoindividuals A and B who are specifically intimate, and another group ofat least two individuals C and D who are also specifically intimate,then a large group of the combination of these individuals A, B, C, andD, and so on.

An exemplary method for determining the distance of relationship (EK41)between given individuals from the cross-correlation calculation betweenindividuals (EA14) to display the distance will be described later (seeFIG. 8).

Next, the calculation based on the infrared data will be described ingreater details. The infrared data includes the information indicatingwhen and who meets someone. The management server 4 uses the infrareddata to analyze the face-to-face record (EI22). The management server 4will then determine the parameter for displaying the organizationstructure based on the face-to-face history (EK43). At this time themanagement server 4 may calculate the distance between given individualsfrom the face-to-face history, in order to determine the parametersbased on the distance. For example, the distance may be calculated suchthat the distance between the individuals becomes shorter (in otherwords the stronger relationship) if the number of times of meeting twoindividuals within a predetermined period of time is as much frequent.

For example, the management server 4 may determine the parameters so asto reflect the sum of total number of the face-to-face meeting of aperson to the size of a node, the number of times of the short-termmeeting of individuals to the distance between nodes, and the number oftimes of the long-term meeting between the given individuals to thewidth of the link. The node herein is a shape displayed for indicatingan individual on the display (CLOD) of a client (CL). The link herein isa line displayed for connecting two nodes. The person who has met thelargest number of times with someone who could be anybody will bedisplayed as the largest node. The combination of persons who have beenmet frequently recently is displayed by two closer nodes. Thecombination of persons who have been met for a long period of time willbe displayed by two nodes connected by a thick link.

The management server 4 may also reflect the property information of auser who wears the sensor node 3 to the display of the organizationstructure. For example, the color of node indicative of a person may bedefined based on the age of the person, the shape of the node indicativeof a person may be defined based on his/her post.

Next, the calculation based on the voice data will be described ingreater details. As have been described above, by using the voice datain place of the acceleration data, the cross-correlation betweenindividuals can be calculated as similar to the calculation based on theacceleration data. The speech feature may be extracted (EV33) byextracting the voice feature from the voice data (EV32) and by analyzingthe feature in combination with the face-to-face data. The speechfeature is the quantity indicative of the voice tone in theconversation, the rhythm of the conversation, or the balance of speech.The balance of speech is the quantity indicating whether one of twopersons speaks in the one-sided manner, or whether both of them speakevenly, and the quantity is extracted based on the voice of twoindividuals.

For example, the management server 4 may determine the display parametersuch that the speech balance is reflected to the angle between nodes.More specifically, for example, when two individuals speak evenly, thenodes indicative of these two individuals may be displayed horizontally.In case in which one of them speaks in one-way, the node indicative ofthe person who is speaking may be displayed above the other nodeindicative of the other person. If the tendency that one of them speaksin the one-way fashion is much intensive, the angle between the lineconnecting these nodes indicative of two persons and the reference line(in the organization structure display (FC31) shown in FIG. 19A, theangle theta AB or theta CD) may be displayed larger. The reference lineherein is the line set in the lateral direction of the display (i.e., inthe horizontal direction). The reference line may or may not bedisplayed.

The organization activity display (BMF) is a process which creates, fromthe organization performance prediction and the organization structureparameters as calculated by the process as have been described above,the index balance indication (FA11), index forecast record (FB21), therepresentation of organization structure (FC31) and the like, thendisplays on the display (CLOD) of the client (CL).

The organization activity (FD41) shown in FIG. 19A is an exemplaryscreen displayed on the display (CLOD) of the client (CL).

In the example shown in FIG. 19A, the display period of time selected,and the units or plural members to be displayed are initially displayed.The unit herein is an organization composed of plural persons. Allmembers belonging to one unit may be displayed, or plural membersconstituting a part of a unit may be displayed. In the example shown inFIG. 19A the result of analysis based on the condition indicated by theperiod of time of display and the unit is displayed by three figures.

In the figure of the index forecast record (FB21), the record of theforecast result of the performance in the “growth” is displayed as anexample. This allows analyzing, by checking with the past actionhistory, what kind of action of a member contributes to the growth ofthe organization, and additionally what is effective for the conversionfrom negative to positive result.

In the organization structure display (FC31), the situation of a smallgroup constituting the organization, the role substantially played bythe persons in the organization, and the balance between givenindividuals may be visualized.

The index balance indication (FA11) indicates the balance configured forset six organization performance prediction. This allows assessing theadvantages and the disadvantages of the current organization.

Embodiment 3

Now the sensor-Net system using the time synchronization scheme inaccordance with a third preferred embodiment of the present inventionwill be described in greater details.

Now referring to FIG. 20, there is shown an applied system for detectingthe focus 2001 of an earthquake by using the sensor-Net system. Forspecifying the focus of an earthquake the grid search method (see forexample non-patent reference document #2) may be used. For specifyingthe location of the focus of earthquake with the precision of less than100 meters by means of the grid search method, more than three sensornodes are required, each of which has an acceleration sensor or avibration sensor, these sensor nodes are to be placed at the distance of100 meters, and the time synchronization must be done at the precisionof 20 milliseconds.

Now referring to FIG. 21 there is shown a system for observing thevibration of piping by using the sensor-Net system. The phase differenceof the waveform 2102 conducted along with the piping 2101 is calculatedby using the sensor-Net system, in order to detect the position of thepressure node and the pressure antinode. This allows specifying thelocation of generating the waveform or calculating the stress applied.To achieve this, it is needed to detect the phase difference of waveformconducting along with the piping at 200 Hz, requiring accordingly thetime synchronization of the sensor nodes at the precision of a fewmilliseconds.

The time synchronization method in accordance with the third preferredembodiment of the present invention for achieving the timesynchronization precision in such a system will be described in greaterdetails herein below.

Now referring to FIG. 22 there is shown a schematic sequential diagramillustrating the time synchronization method in accordance with thethird preferred embodiment of the present invention for decreasing theerror of time when the sensor node 3 is connected to the gateway node 1through the router node 2 in a multi-hop connection.

The gateway node obtains the time t1 from its own real time clock 406(2201), and transmits t1 to the router node. The router, upon receptionof the time t1, obtains immediately the time t2 from its own real timeclock 306 (2202), to calculate the difference between t2 and t1(ΔT1=t2*t1) (2203). Next, the router obtains the time t3 from its ownreal time clock 306 (2204), and transmits the ΔT1 and t3 to the gatewaynode. The gateway node which has received the ΔT1 and t3 obtainsimmediately the time t4 from its own real time clock 406 (2205), thenuses ΔT1, t3 and t4 to calculate the delay (2*Δt=t4−t3+ΔT1) (2206). Thuscalculated Δt is the delay at the time of setting the time in thegateway node and in the router. If the delay (t varies each time it ismeasured, the precision may be improved by calculating the mean of (t bymeasuring plural times. If a router is connected to another router, thedelay may also be calculated between these routers.

Next, the base station gateway node obtains the time from its own realtime clock 406 regularly or at the timing specified by the user (2207),to send a setTime command (2208). At this time the current time t5obtained from its own real time clock 406 and the delay (t are sent atthe same time in a setTime command. The router node which receives thissetTime command uses the difference between the time t5 included in thesetTime command and the delay (t(T2=t5−(t) to set or correct its ownreal time clock (2209). At the time of receiving the polling (2210) fromthe sensor node the router obtains the time t6 from the real time clockof the router (2211) and sends the time t6 and the delay (t as thesetTime command (2212). The sensor node which receives the setTimecommand uses the difference between the time t6 and the delay(t(T3=t6−(t) to set or correct its own real time clock.

The primary cause of the delay in this method is the processing timefrom the time when the firmware of the base station gateway node and therouter obtain the time from the real time clock to the time whentransmitting through their RF transceiver, and the processing time fromthe time when receiving at the RF transceiver to the time when obtainingthe time from the real time clock, and in case in which no interrupt isincluded the delay will be at the level of tens milliseconds. The samecircuit is used for the real time clock, the microprocessor, and the RFtransceiver in the base station gateway node, the router, and the sensornode. Therefore the delay between the router and the sensor node can beconsidered to be almost the same as the delay between the base stationgateway node and the router.

If there are plural routers connected to a base station gateway node,the dispersion of the delay caused by the individual variability will bedecreased by calculating the delay (t between the base station gatewaynode and all routers and by calculating the mean value.

If the data transmission is failed on the wireless medium, thetransmission will be repeated at the transmission interval of a fewmilliseconds at most three times. The error in the present methodtherefore is the error caused by the wireless retransmission, which isin the range of a few milliseconds to 10 milliseconds.

The sensor-Net in a meshed type multi-hop has the advantage that thecommunication path can be freely selected. By using this, the timeconfiguration is performed by avoiding the path having a larger delay toimprove the time precision. More specifically, the router stores thedelay (t to calculate the variance ((t of the (t each time the routerreceives a setTime command. The ((t can be considered to as thecommunication cost. To configure the time, the time is set by usingpreferentially the path having a lower ((t in order to achieve a highprecision time configuration.

As can be appreciated from the foregoing description, in accordance withthe preferred embodiments of the present invention, as the sensor nodemay set the time while maintaining its intermittent operation, and thetime is set only when the time in the router is synchronized with thereference time, the deviation of the time may be suppressed to theminimum while at the same time any waste waiting time is saved, as aresult the power consumption can be lowered and more specifically whenthe sensor node is powered by a battery the life of the battery can beextended.

EFFECT OF THE INVENTION

In accordance with the present invention, the power consumption in thesensor-Net system may be saved, more specifically the battery life isextended if the sensor node is battery-operated.

The foregoing description of the preferred embodiments of the inventionhas been presented for purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed, and modifications and variations are possible in lightof the above teachings or may be acquired from practice of theinvention. The embodiments are chosen and described in order to explainthe principles of the invention and its practical application to enableone skilled in the art to utilize the invention in various embodimentsand with various modifications as are suited to the particular usecontemplated. It is intended that the scope of the invention be definedby the claims appended hereto, and their equivalents.

It is further understood by those skilled in the art that the foregoingdescription is some preferred embodiments of the disclosed system andmethod and that various changes and modifications may be made in theinvention without departing from the spirit and scope thereof.

1. A sensor-Net system, comprising a base station gateway node, a routernode connected to the base station gateway node in a wirelesscommunication, and a sensor node connected to the base station gatewaynode and to the router node in a wireless communication, the basestation gateway node and the router node being in operation all thetime, the sensor node being in intermittent operation, wherein therouter node transmits, when setting the clocks of the gateway node, therouter node, and the sensor node, at the timing of being requested witha command transmission from the sensor node, the time setting commandbased on the latest time of the router node to the sensor noderequesting the command transmission; and the sensor node, upon receptionof the latest time from the router node, sets the time based on thelatest time of the router node.
 2. A sensor-Net system according toclaim 1, wherein the gateway node has a plurality of the router nodesand the sensor nodes as siblings, and has a management table formanaging the sibling router nodes and the sibling sensor nodes; and thegateway node, upon reception of a time setting command from a managementserver connected through a network, refers to the management table toexpand immediately the time setting command to the sibling router nodesto synchronize the time in the router nodes.
 3. A sensor-Net systemaccording to claim 1, wherein the router node has a storage unit forstoring a time configuration flag each corresponding to all of thesibling sensor nodes; the router node, receiving a time setting commandfrom the gateway node, at the timing of setting the latest time of therouter node, turns on the time configuration flags held in the storageunit; the router node, upon reception of the command transmissionrequest from the sensor node, checks to see the ON or OFF status of thetime configuration flag, and transmits, only when the time configurationflag is ON, the time setting command based on the latest time of therouter node to the sensor node having transmitted the commandtransmission request; the router node turns off the time configurationflag held in the storage unit at the timing of receiving the reply tothe time setting command.
 4. A sensor-Net system according to claim 2,wherein the router node has a storage unit for holding a timeconfiguration flag each corresponding to all of the sibling sensornodes; the router node, receiving the time setting command from thegateway node, turns on the time configuration flag held in the storageunit, at the timing of setting the latest time of the router node; therouter node, when receiving the command transmission request from thesensor node, checks to see the ON or OFF status of the timeconfiguration flag, and transmits, only when the time configuration flagis ON, the time setting command based on the latest time of the routernode to the sensor node having sent the command transmission request.the router node turns off the time configuration flag held in thestorage unit at the timing of receiving the reply to the time settingcommand.
 5. A sensor-Net system according to claim 3, wherein the sensornode, based on the latest time of the sensor node set based on the timesetting command from the router node, adds the time to the observationvalue held, then transmits the observation value to the router node. 6.A sensor-Net system according to claim 4, wherein the sensor node, basedon the latest time of the sensor node set based on the time settingcommand from the router node, adds the time to the observation valueheld, then transmits the observation value to the router node.
 7. Asensor-Net system according to claim 5, wherein the sensor node, afterhaving sent the observation value to the router node, stores theobservation value having the time added into the storage unit of thesensor node, then enters into sleep mode of the intermittent operation.8. A sensor-Net system according to claim 6, wherein the sensor node,after having sent the observation value to the router node, stores theobservation value having the time added into the storage unit of thesensor node, then enters into sleep mode of the intermittent operation.9. A sensor-Net system according to claim 5, further comprising: amanagement server connected to the gateway node through a network,including a communication unit for connecting to the network, aprocessing unit, and a storage unit; wherein the management serverreceives the observation value received by the router node through thegateway node for storing in an observation value storage unit in thestorage unit.
 10. A sensor-Net system according to claim 6, wherein themanagement server is made up a communication unit for connecting to thenetwork, a processing unit, and a storage unit; the management serverreceives the observation value received by the router node through thegateway node for storing in an observation value storage unit in thestorage unit.
 11. A sensor-Net system according to claim 9, wherein theprocessing unit of the management server calculates the influencebetween a first wearer wearing the first sensor node and a second wearerwearing the second sensor node based on the observation valuetransmitted by the first sensor node and the observation valuetransmitted by the second sensor node, both stored in the observationvalue storage unit.
 12. A sensor-Net system according to claim 10,wherein the processing unit of the management server calculates theinfluence between a first wearer wearing the first sensor node and asecond wearer wearing the second sensor node based on the observationvalue transmitted by the first sensor node and the observation valuetransmitted by the second sensor node, both stored in the observationvalue storage unit.
 13. A sensor-Net system according to claim 11,wherein the first and second sensor nodes have an acceleration sensor,respectively; the first and second sensor nodes transmit the output dataof the acceleration sensor as the observation value; the processing unitof the management server determines the correlation of action betweenthe first and second wearers based on the output data of theacceleration sensor in order to calculate the influence.
 14. Asensor-Net system according to claim 12, wherein the first and secondsensor nodes have an acceleration sensor, respectively; the first andsecond sensor nodes transmit the output data of the acceleration sensoras the observation value; the processing unit of the management serverdetermines the correlation of action between the first and secondwearers based on the output data of the acceleration sensor in order tocalculate the influence.
 15. A sensor-Net system, comprising a gatewaynode, and a sensor node connected to the gateway node through a wirelesscommunication, the gateway node being in operation all the time, thesensor node being in intermittent operation, wherein the sensor nodeissues a time request command on a regular basis or at the timing ofconnecting to the gateway node, and invokes its internal timer at thetime when receiving a reply to the time request command from the gatewaynode; the gateway node obtains a reference time at the time whenreceiving the time request command from the sensor node, and transmitsthe reference time to the sensor node at the time when receiving a nextcommand transmission request from the sensor node; the sensor node stopsthe timer at the time when receiving the reference time, calculates theactive time of the timer from the difference between the timer stoppingtime and the timer activated time, and then performs the timeconfiguration by adding the reference time received from the gatewaynode to the timer activated time.
 16. A sensor-Net system according toclaim 15, wherein the sensor node performs the time setting, andthereafter transmits the observation values stored in the sensor node tothe gateway node.
 17. A sensor-Net system according to claim 16, furthercomprising: a management server connected to the gateway node through anetwork, including a communication unit for connecting to the network, aprocessing unit, and a storage unit; wherein the management serverreceives the observation value received by the gateway node from thegateway node in order to store in the observation value storage unit inthe storage unit.
 18. A sensor-Net system according to claim 17, whereinthe processing unit of the management server calculates the influencebetween a first wearer wearing the first sensor node and a second wearerwearing the second sensor node based on the observation valuetransmitted by the first sensor node and the observation valuetransmitted by the second sensor node, both stored in the observationvalue storage unit.
 19. A sensor node connected through a wirelesscommunication to a gateway node being in operation all the time, forintermittently operating, comprising: a processing unit, a storage unit,an RF transceiver unit, and a real time clock, wherein the processingunit issues a time request command on a regular basis or at the timingof connecting to the gateway node, and invokes its internal timer at thetime when receiving a reply to the time request command from the gatewaynode; the processing unit, after issuing the time request command, whentransmitting a next command transmission request to the gateway node,receives a reference time obtained by the gateway node at the time whenreceiving the time request command from the sensor node; the sensor nodestops the timer at the time when receiving the reference time,calculates the active time of the timer from the difference between thetimer stopping time and the timer activated time, and then sets the timeof the real time clock by adding the reference time received from thegateway node to the timer activated time.
 20. A sensor node according toclaim 19, wherein the processing unit is a microprocessor incorporatinga timer which is operable in a low power consumption mode; and the timerincorporated in the microprocessor is used as the timer to calculate theactivated time.